Engineers Use Rocket Science for Self-Sufficient Wastewater Treatment

crop dusting plane photo

Photo via divemasterking2000 via Flickr CC

Nitrates are commonly found in groundwater, ending up there after they're used for fertilizing crops or from storm-water run-off. Typically a contaminate to worry about, a group of engineers from Stanford University have figured out how to turn the problem of nitrates in the water in to a possible solution for energy generation. While their design started out as a nitrous oxide thruster for spacecraft, they figured out how it could also be used at wastewater treatment plants to turn decompose nitrous oxide gas into nothing but hot air. Stanford reports that two of their engineers -- one a rocket engineer who has spent five years creating thrusters that run on nitrous oxide and the other an expert in wastewater management -- have created a design that can carve down the carbon footprint of wastewater treatment plants with "a new sewage treatment process that would actually increase the production of two greenhouse gases - nitrous oxide (aka, "laughing gas") and methane - and use the gases to power the treatment plant."

"Normally, we want to discourage these gases from forming," said Craig Criddle, a professor of civil and environmental engineering and senior fellow at the Woods Institute for the Environment at Stanford. "But by encouraging the formation of nitrous oxide, we can remove harmful nitrogen from the water and simultaneously increase methane production for use as fuel."

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Part of the cradle-to-cradle design manifesto includes thinking of wastes as resources that are simply out of place. That is the take the engineers have on nitrates as well.

"For too long we've thought of treatment plants as places where we remove organic matter and waste nitrogen," one of the scientists states. "We need to view these wastes as resources, not simply something to dispose of."

rocket thruster image

Rocket Thruster Design; Image via Brian Cantwell, Stanford University

Now with this rocket thruster design, nitrates in the wastewater can be used to generate nitrus oxide and methane, with the methane harvested to run the plant, the nitrus oxide burned in a rocket thruster to break it down into clean hot air, and the nitrates safely removed from the water through the whole process. It's an ideal set-up for a self-sustaining wastewater facility even in locations that don't currently have an energy source such as rural or third world areas.

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